STIR Charter (discussion) - PowerPoint Presentation

Slide1

STIR Charter (discussion)

STIR

BoF

Berlin, DE

7/30/2013Slide2

For reference

This is a snapshot of the 7/23 charter version

Obviously this does not capture any discussion today

No need to excessively wordsmith here

This is available on the STIR list for your perusal

Chairs will ask for hums later, but now let’s chatSlide3

Preamble

Over the last decade, a growing set of problems have resulted from

the lack

of security mechanisms for attesting the origins of real-

time communications

.  As with email, the claimed source identity of a

SIP request

is not verified, and this permits unauthorized use of

source identities

as part of deceptive and coercive activities, such

as

robocalling

(bulk unsolicited commercial communications),

vishing

(

voicemail hacking, and impersonating banks) and swatting (

impersonating callers

to emergency services to stimulate unwarranted large scale

law enforcement

deployments).  This working group will define a

deployable mechanism

that verifies the authorization of the calling party to

use a

particular telephone number.Slide4

Postamble

SIP is one of the main VoIP technologies used by parties that want

to present

an incorrect origin, in this context an origin telephone

number. Several

previous efforts have tried to secure the origins of

SIP communications

, including RFC 3325, RFC 4474, and the VIPR working

group. To

date, however, true validation of the source of SIP calls has not

seen any

appreciable deployment.  Several factors contributed to this lack

of success

, including: failure of the problem to be seen as critical at

the time

; lack of any technical means of producing a proof of authority

over telephone

numbers; misalignment of the mechanisms proposed by RFC

4474 with

the complex deployment environment that has emerged for SIP; lack

of end

-to-end SIP session establishment; and inherent operational

problems with

a transitive trust model.  To make deployment of this solution

more likely

, consideration must be given to latency, real-time performance

, computational

overhead, and administrative overhead for the

legitimate call

source and all verifiers.Slide5

The plan (wall o’ text)

As its first work item, the working group will specify a SIP header-

based authorization

mechanism to verify the originator of a SIP session

is authorized

to use the claimed source telephone number, where the

session is

established with SIP end to end.  This is called an in-band

mechanism. The

mechanism will use a canonical telephone number

representation specified

by the working group, including any mappings that might

be needed

between the SIP header fields and the canonical telephone

number representation

.  The working group will consider choices for

protecting identity

information and credentials used, but will likely be based on

a digital

signature mechanism that covers a set of information in the

SIP header

fields, and verification will employ a credential that

contains the

public key and is associated with the one or more telephone

numbers. In

order to be authoritative, credentials used with this mechanism

will be

derived from existing telephone number assignment and

delegation models

.  That is, when a telephone number or range of telephone

numbers is

delegated to an entity, relevant credentials will be generated (

or modified

) to reflect such delegation.  The mechanism must allow

a telephone

number holder to further delegate and revoke use of a 

telephone

number without compromising the global delegation scheme.Slide6

Limitations and Warranties

The mechanism must allow

parties who

are not delegated a telephone number, but are authorized by

the entity

who is delegated the number, to place calls using the identity.

After completing the in-band mechanism, the working group will

consider session

establishment where there are one or more non-SIP hops,

most likely

using an out-of-band authorization mechanism.  However,

the in

-band and the out-of-band mechanisms should share as much in

common as possible

, especially the credentials.

Expansion of the authorization mechanism to identities using

the

user

@domain

form is

deferred since the main focus of the working group is

to develop

a solution for telephone numbers.Slide7

Disclaimers and Pleasantries

The working group will coordinate with the Security Area on

credential management

.

The working group will coordinate with other working groups in the

RAI Area

regarding signaling through existing deployments.

Authentication and authorization of identity is closely linked

to privacy

, and these security features frequently come at the cost

of privacy

.  This working group is not chartered to mandate the presence

of identity

in SIP requests, and to the extent feasible it will

find privacy

-friendly solutions that leak minimal information about calls

to third

parties.Slide8

Inputs (won’t be in the charter)

  Private Extensions to the Session Initiation Protocol (SIP

) for

Asserted Identity within Trusted

Networks (RFC 3325)

  Enhancements for Authenticated Identity Management in

the

  Session Initiation Protocol (SIP

) (RFC 4474)

  Secure Call Origin

Identification

http

://tools.ietf.org/html/draft-cooper-iab-secure-origin-00

  Secure Origin Identification: Problem Statement, Requirements

,

and

Roadmap

http

://tools.ietf.org/html/draft-peterson-secure-origin-ps-00

  Authenticated Identity Management in the Session

Initiation

Protocol (SIP)

http

://tools.ietf.org/html/draft-jennings-dispatch-rfc4474bis-00Slide9

Outputs

The working group will deliver the following:

-

A

problem statement detailing the deployment environment

and

  situation that motivate work on secure telephone identity

- A

mechanism document describing the SIP end-to-end with

telephone

 number-based identities 

A

document describing the credentials required to

support telephone

number identity authentication

A

fallback mechanism to allow out-of-band identity

establishment

during call setupSlide10

Milestones

Sep 2013   Submit problem statement for Informational

Nov 2013   Submit in-band mechanism for Proposed Standard

Feb 2014   Submit credential specification for Proposed Standard

Jun 2014   Submit fallback for Proposed Standard